High elastic aluminum alloy and method for producing the same

ABSTRACT

Disclosed is an aluminum alloy, including: about 14˜20 wt % of Si; about 2˜7.5 wt % of Ti; about 1˜3 wt % of B; and a balance of Al as a main component, wherein wt % are based on the total weight of the aluminum alloy and wherein a ratio of Ti/B is about 2˜2.5:1.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119(a) the benefit of Korean Patent Application No. 10-2012-0145787 filed Dec. 13, 2012, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a high elastic aluminum alloy, particularly to such an alloy whose elasticity is remarkably improved by maximizing the formation of a boride compound and adding CNT thereto, and a method of manufacturing the same.

2. Description of the Related Art

Conventionally, in providing alloys, the various alloy ingredients are controlled so as to impart desired characteristics.

For example, when only silicon (Si) is used to make a high elastic alloy, the elasticity of the alloy cannot be sufficiently improved, and the silicon (Si) particles become coarse. As such, it is difficult to produce a highly elastic alloy because of the coarse silicon (Si) particles.

Further, conventional aluminum (Al) composite materials are expensive, even though they are formed into powder using reinforced metal compounds or carbon nanotubes (CNTs).

Further, when powdered reinforced particles are introduced into a casting process, there are problems of loss, wettability and dispersity in a molten aluminum (Al) solution. Further, when only reinforced particles are added to a base alloy without otherwise improving the base alloy, the amount of reinforced particles must be increased in order to attain a desired elasticity. This results in causing several problems, including increased cost, increase difficulty in control over the process and the like.

In order to provide alloys with improved elasticity, various technologies have been developed. For example, such technologies have included maximizing the formation of a boride compound which plays an important role in the improvement of elasticity, adding CNT to a high elastic alloy to thereby increase elasticity, preventing CNT from being damaged in a high-temperature molten aluminum solution, and uniformly dispersing the boride compound formed by the spontaneous reaction with CNT in the aluminum molten solution.

Korean Unexamined Patent Application Publication No. 10-2012-0059256 describes “an aluminum casting alloy and a method of manufacturing the same.” It is described in KR 10-2012-0059256 A that “the present invention relates to an aluminum alloy including aluminum 81˜93 wt %, silicon 5˜13 wt %, titanium 1˜3 wt % and boron 1˜3 wt %. The aluminum alloy of the present invention has high elasticity compared to conventional aluminum alloys although it does not include expensive materials such as carbon nanotubes (CNTs) and the like. Further, conventional aluminum alloys can be applied only to a low-pressure casting process, whereas the aluminum alloy of the present invention can be applied to all general casting processes including a high-pressure casting process.”

However, this technology does not solve the above problems of loss, wettability and dispersity in a molten aluminum (Al) solution when powdered reinforced particles are introduced into a casting process. Further, when the amount of reinforced particles is increased, this technology does not adequately decrease costs, process control difficulty or the like.

It is to be understood that the foregoing description is provided to merely aid the understanding of the present invention, and does not mean that the present invention falls under the purview of the related art which was already known to those skilled in the art.

SUMMARY OF THE INVENTION

Accordingly, the present invention provide a highly elastic aluminum alloy whose elasticity is remarkably improved by maximizing the formation of a boride compound and adding CNT thereto, and a method of manufacturing the same.

In order to accomplish the above object, an aspect of the present invention provides an aluminum alloy, including: about 14˜20 wt % of Si; about 2˜7.5 wt % of Ti; about 1˜3 wt % of B; and a balance of Al as a main component, wherein wt % are based on the total weight of the alloy composition, and wherein a ratio of Ti/B is about 2˜2.5:1.

According to various embodiments, the aluminum alloy is formed by continuous casting.

According to various embodiments, the aluminum alloy is prepared using aluminum mother alloys of Al-(5˜10 wt %)Ti and Al-(2˜10 wt %)B.

According to various embodiments, the aluminum alloy further includes about 2˜7 vol % of CNT.

According to various embodiments, the CNT is coated with one or more metal oxide, which can be selected from any known metal oxides.

Another aspect of the present invention provides a method of manufacturing the aluminum alloy, including the steps of: coating CNT with one or more metal oxides; introducing the CNT into an aluminum molten solution together with inert gas and stirring the mixture; and forming the aluminum alloy using continuous casting.

According to various embodiments, the CNT is completely coated with one or more metal oxide to a thickness of about 20˜50 nm.

According to various embodiments, the stirring is performed at a rotation speed of about 500˜1500 rpm.

According to various embodiments, in the step of forming the aluminum alloy, the aluminum molten solution is vibrated on a casting table during the continuous casting before being injected into a mold.

Other aspects and exemplary embodiments of the invention are discussed infra.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a graph showing the elasticity of a high elastic aluminum alloy according to an embodiment of the present invention;

FIG. 2 is a schematic view showing a stirring apparatus used to manufacture a high elastic aluminum alloy according to an embodiment of the present invention; and

FIG. 3 is a flowchart showing a method of manufacturing a high elastic aluminum alloy according to an embodiment of the present invention.

REFERENCE NUMERALS

S100: coating

S200: stirring

S500: forming

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about”.

FIG. 1 is a graph showing the elasticity of a high elastic aluminum alloy according to an embodiment of the present invention, FIG. 2 is a schematic view showing a stirring apparatus used to manufacture a high elastic aluminum alloy according to an embodiment of the present invention, and FIG. 3 is a flowchart showing a method of manufacturing a high elastic aluminum alloy according to an embodiment of the present invention.

According to an exemplary embodiment, the high elastic aluminum alloy of the present invention includes about 14˜20 wt % of Si, about 2˜7.5 wt % of Ti, about 1˜3 wt % of B; and a balance of Al as a main component, wherein the wt % are based on the total weight of the aluminum alloy composition. According to various embodiments, the ratio of Ti/B is about 2˜2.5:1.

According to the present invention, it has been found that when the aluminum alloy has the above composition and ratio of Ti/B, the formation of a boride compound that plays an important role in the improvement of elasticity can be maximized.

According to various embodiments, in order to maintain the desired ratio of Ti/B and naturally induce a TiB₂ compound, the aluminum alloy may be prepared using two aluminum mother alloys, Al-(5˜10 wt %)Ti and Al-(2˜10 wt %)B. Al-(5˜10 wt %)Ti includes about 5˜10 wt % of Ti and balance of Al as a main constituent. The other aluminum mother alloy, Al-(2˜10 wt %)B includes about 2˜10 wt % of B and balance of Al as a main constituent.

Further, when the formation of the boride compound is maximized using the present method and compositions, the elasticity, mechanical properties (strength, wear resistance) and workability of a base alloy can be improved.

The elastic modulus of conventional aluminum alloy (A390: Si 17 wt %) is about 85 GPa, which is much less than the elastic modulus of the aluminum alloys in accordance with the present invention. For example, an aluminum alloy (Al-16Si-2.3Ti-1B) of the present invention demonstrates an elastic modulus of 102 Gpa, and another aluminum alloy (Al-20Si-2.3Ti-1B) of the present invention demonstrates an elastic modulus of about 106 GPa.

The compositions of the aluminum alloy according to the present invention and a conventional aluminum alloy, which differ only in the ratio of Ti and B, are given in Table 1 below.

TABLE 1 Si Fe Cu Mn Mg Ni Zn Ti B Al Conventional A390 16-18 0.5 4.0-5.0 0.1 0.45-0.65 — 0.1 0.2 — Bal. technology Invention Invention 14-20 — — — — — — 2-7.5 1-3 Bal. Example 16-18 0.5 4.0-5.0 0.1 0.45-0.65 — 0.1 2-7.5 1-3 Bal. (A390 applied)

As shown in Table 1 above, unlike the conventional aluminum alloy, the aluminum alloy of the present invention includes about 2˜7.5 wt % of Ti, about 1˜3 wt % of B and a balance of Al.

Further, the results of formation of boride according to embodiments of the present invention are given in Table 2.

TABLE 2 Ti:B = 1:1 Ti:B = x:1 Alloy TiB₂ Alloy TiB₂ Content 1 wt % Al—1Ti—1B 1.45 Al—2.3Ti—1B 3.21 of B 2 wt % A2—1Ti—2B 2.9 Al—4.5Ti—2B 6.3 3 wt % Al—3Ti—3B 4.36 Al—6.7Ti—3B 9.64

As shown in Table 2, according to the present invention, the amount of boride is present in the range of 1.45 to 9.64. From the results, it is preferred to provide the ratio of Ti/B between about 2˜2.5:1.

FIG. 1 is a graph showing the elasticity of a high elastic aluminum alloy according to an embodiment of the present invention. As demonstrated in the graph of FIG. 1, when the content of TiB2 is 9.64%, the elastic modulus of an aluminum alloy is increased 45% from 68 GPa to 98.5 GPa.

The aluminum alloy of the present invention can be formed by any suitable methods, and is preferably formed by continuous casting. Continuous casting is a casting method of continuously injecting molten metal into a mold and solidifying the injected molten metal. Such casting is generally used to produce plate-shaped, bar-shaped or line-shaped billets. In the continuous casting method, a molten solution is poured into the top of a mold to form an ingot, and the ingot is continuously rapidly cooled and drawn to produce long billets having a length of several meters to several tens of meters. When an alloy is made by continuous casting, the temperature of a tundish (i.e. a broad, open container with one or more holes in the bottom conventionally used in casting metals) must be controlled at the time of solidifying a molten solution (Al—Si—Mg—Cu) because the molten solution may be changed.

When the molten solution is charged in the tundish, the inlet of the tundish is heated to about 650° C. or more to prevent the molten solution from being solidified by rapid cooling, and the temperature of the outlet of the tundish is maintained at about 300˜350° C. to discharge the molten solution in a mush state. This procedure is necessary for maintaining the shape of billets without downwardly flowing the molten solution continuously injected into the top of the tundish. Continuous casting exhibits a rapid cooling rate compared to other casting methods, so this continuous casting is advantageous in increasing the content of solute atoms and in improving the fineness and uniformity of the texture of the alloy.

According to the present invention, elasticity of an alloy is maximized by adding CNT to a high elastic alloy, by preventing the CNT from being damaged in a high-temperature molten aluminum solution, and by uniformly dispersing the boride compound formed by the spontaneous reaction with CNT in the aluminum molten solution.

According to various embodiments, the aluminum alloy may further include about 2˜7 vol % of CNT. The CNT may be coated with one or more metal oxides, which can be selected from any known metal oxides.

According to an exemplary embodiment of the present invention, when 2.3Ti-1B and 5 vol % of CNT were added to Al-16Si, the final elastic modulus thereof was 112.5 Gpa. Further, when 2.3Ti-1B and 5 vol % of CNT were added to Al-20Si, the final elastic modulus thereof was 118.5 GPa.

In this case, it is preferred that the content of CNT be about 2˜7 vol %. When CNT is added in an amount of at least 2 vol %, the elastic modulus of the aluminum alloy can be adjusted to 105 GPa, thus obtaining an aluminum alloy having physical properties equal to those of cast iron. However, when CNT is used in an amount of more than 7 vol % during casting, there is a problem in that the CNT is not sufficiently melted and dispersed. As a result, the thus obtained aluminum alloy is not suitable as a material for casting.

FIG. 3 is a flowchart showing a method of manufacturing a high elastic aluminum alloy according to an embodiment of the present invention. The method of manufacturing a high elastic aluminum alloy according to the present invention generally includes the steps of: coating CNT with metal oxide (S100); introducing the CNT into an aluminum molten solution together with inert gas and stirring the mixture (S200); and forming the aluminum alloy using continuous casting (S500).

In particular, first, an aluminum molten solution is prepared that preferably uses aluminum mother alloys of Al-(5˜10 wt %)Ti and Al-(2˜10 wt %)B, wherein the ratio of Ti/B is adjusted in the range of about 2˜2.5:1.

Subsequently, CNT is coated with one or more metal oxides, such as SiO₂, TiO₂ or the like, to a thickness of about 20˜50 nm to prevent the CNT from being damaged in the high-temperature aluminum molten solution (S100). Preferably, the CNT is completely coated with the one or more metal oxides.

Subsequently, the coated CNT is introduced into the aluminum molten solution 10 together with inert gas, and then stirred at a high rotation speed of about 500˜1500 rpm, for example, using a double stirrer 20 shown in FIG. 2, to uniformly disperse the CNT and the boride compound in the aluminum molten solution 10 (S200).

Subsequently, thermal insulation and runner transportation are performed (S300), followed by vibrating the aluminum molten solution on a casting table during the continuous casting before injection into a mold (S400). The casting table contributes to the improvement of uniformity of reinforced particles by vibrating the aluminum molten solution before it is injected into a mold.

As such, the uniformity of the high elastic aluminum alloy can be improved by the rapid cooling rate in continuous casting, the high-speed rotation of the double stirrer and the vibration of the aluminum molten solution on the casting table.

As described above, according to the present invention, the improvement of elasticity of the aluminum alloy can be maximized by maximizing the formation of a boride compound and by adding CNT to the high elastic alloy

Further, according to the present invention, it is possible to prevent CNT from being damaged in a high-temperature molten aluminum solution. Still further, according to the present invention, the boride compound formed by the spontaneous reaction with CNT can be uniformly dispersed in the aluminum molten solution.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 

What is claimed is:
 1. An aluminum alloy, comprising: about 14˜20 wt % of Si; about 2˜7.5 wt % of Ti; about 1˜3 wt % of B; and a balance of Al as a main component, wherein wt % are based on the total weight of the aluminum alloy, and wherein a ratio of Ti/B is about 2˜2.5:1.
 2. The aluminum alloy of claim 1, wherein the aluminum alloy is formed by continuous casting.
 3. The aluminum alloy of claim 1, wherein the Ti, B and Al components comprise aluminum mother alloys of Al-(5˜10 wt %)Ti and Al-(2˜10 wt %)B.
 4. The aluminum alloy of claim 1, further comprising: about 2˜7 vol % of CNT.
 5. The aluminum alloy of claim 4, wherein the CNT is coated with one or more metal oxides.
 6. A method of manufacturing the aluminum alloy of claim 4, comprising the steps of: coating CNT with one or more metal oxides; introducing the CNT into an aluminum molten solution together with inert gas and stirring to form a mixture; and forming the aluminum alloy from the mixture using continuous casting.
 7. The method of claim 6, wherein the CNT is coated with one or more metal oxides to a thickness of about 20˜50 nm.
 8. The method of claim 6, wherein the stirring is performed at a rotation speed of about 500˜1500 rpm.
 9. The method of claim 6, wherein, in the step of forming the aluminum alloy, the aluminum molten solution is vibrated on a casting table during the continuous casting before it is injected into a mold. 